Hitherto, in general, coated tools in which the surfaces of tool bodies made of tungsten carbide (hereinafter, referred to as WC)-based cemented carbide, titanium carbonitride (hereinafter, referred to as TiCN)-based cermet, or a cubic boron nitride (hereinafter, referred to as cBN)-based ultra-high pressure sintered body (hereinafter, collectively referred to as a tool body) are coated with a Cr—Al-based or Ti—Al-based complex nitride layer as a hard coating layer through a physical vapor deposition method are known, and it is known that these coated tools exhibit excellent wear resistance.
However, although the coated tool coated with the Cr—Al-based or Ti—Al-based complex nitride layer in the related art has relatively excellent wear resistance, in a case of using the coated tool under high-speed intermittent cutting conditions, abnormal wear such as chipping easily occurs. Therefore, various suggestions for an improvement in the hard coating layer have been made.
For example, Japanese Unexamined Publication No. 2014-208394 discloses that, in order to improve chipping resistance and wear resistance during high-speed intermittent cutting of stainless steel or a Ti alloy, a hard coating layer formed of a lower layer, an intermediate layer, and an upper layer is provided on a surface of a tool body, the lower layer has a predetermined average layer thickness and is configured with a TiAl compound having a cubic structure formed of one layer or more layers of a Ti1-xAlXN layer, a Ti1-XAlXC layer, and a Ti1-XAlXCN layer (X is a content ratio (atomic ratio) of Al and satisfies 0.65≤X≤0.95), the intermediate layer has a predetermined average layer thickness and is configured with a CrAl compound having a cubic structure formed of one layer or more layers of a Cr1-YAlYN layer, a Cr1-YAlYC layer, and a Cr1-YAlYCN layer (Y is a content ratio (atomic ratio) of Al and satisfies 0.60≤Y≤0.90), and the upper layer is configured with Al2O3 having a predetermined average layer thickness, thereby improving adhesion strength between the lower layer and the upper layer and improving chipping resistance and wear resistance.
Japanese Unexamined Publication No. 2014-198362 discloses that, in order to improve chipping resistance and wear resistance during high-speed intermittent cutting of precipition hardening stainless steel or a heat-resistant alloy such as Inconel, a hard coating layer formed of a lower layer, an intermediate layer, and an upper layer is provided on a surface of a tool body, the lower layer is configured with a Ti compound having a cubic crystal structure formed of one layer or more layers of a Ti1-XAlXN layer, a Ti1-XAlXC layer, and a Ti1-XAlXCN layer (X is a content ratio of Al and an atomic ratio and satisfies 0.65≤X≤0.95) having a predetermined average layer thickness, the intermediate layer is configured with a Cr compound having a cubic structure formed of one layer or more layers of a Cr1-YAlYN layer, a Cr1-YAlYC layer, and a Cr1-YAlYCN layer (Y is a content ratio of Al and an atomic ratio and satisfies 0.60≤Y≤0.90) having a predetermined average layer thickness, and the upper layer is configured with Al2O3 having fine holes having predetermined hole diameter and hole density and an average layer thickness, thereby improving adhesion strength between the lower layer and the upper layer, setting the upper layer as an Al2O3 layer including fine holes having predetermined hole diameter and hole density, relieving mechanical and thermal shock, and improving chipping resistance and wear resistance.
Japanese Unexamined Publication No. 2009-56539 discloses that, in order to increase fracture resistance of a hard coating layer during heavy cutting of steel or cast iron during which high loads are exerted on a cutting edge, a hard coating layer formed of a (Al1-XCrX)N (here, X is an atomic ratio and is 0.3 to 0.6) layer on a surface of a tool body, crystal orientation and a constituent atom-sharing lattice point distribution type are formed in which, in an inclined angle frequency distribution graph drawn by measuring an inclined angle formed by a normal line of a {100} plane with respect to a normal line of a polished surface as a surface of the tool body, a highest peak is present in an inclined angle section of 30 to 40 degrees, a sum of frequencies thereof is equal to or greater than 60% over all frequency, and in a constituent atom-sharing lattice point distribution graph drawn by measuring an inclined angle formed by a normal line of a {112} plane with respect to a normal line of a polished surface as a surface, a highest peak is present in Σ3, and a sum of frequencies thereof is equal to or greater than 50% over all frequency, thereby improving high-temperature strength of the (Al1-XCrX)N layer and improving fracture resistance of the hard coating layer during the heavy cutting.
Japanese Unexamined Publication No. 2006-82207 discloses a surface-coated cutting tool including a tool body and a hard coating layer formed on the body, in which the hard coating layer includes a compound configured with any one or both elements of Al and Cr, at least one kind of element selected from the group consisting of 4a, 5a, and 6a group elements of the periodic table and Si, and at least one kind of element selected from the group consisting of carbon, nitrogen, oxygen, and boron, and chlorine, thereby rapidly improving wear resistance and oxidation resistance of the hard coating layer.
Japanese Unexamined Publication No. 2011-516722, for example, discloses that by performing chemical vapor deposition in a mixed reaction gas of TiCl4, AlCl3, and NH3 in a temperature range of 650° C. to 900° C., a (Ti1-xAlx)N layer in which a value of a content ratio x of Al is 0.65 to 0.95 can be deposited. However, this literature is aimed at further coating the (Ti1-xAlx)N layer with an Al2O3 layer and thus improving a heat insulation effect. Therefore, effects regarding the formation of the (Ti1-xAlx)N layer in which the value of x is increased to 0.65 to 0.95 on cutting performance are not disclosed.
Japanese Unexamined Publication No. 2011-513594 suggests that the heat resistance and fatigue strength of a coated tool are improved by coating a TiCN layer and an Al2O3 layer as inner layers with a (Ti1-xAlx)N layer (here, x is 0.65 to 0.9) having a cubic crystal structure or a cubic crystal structure including a hexagonal crystal structure as an outer layer by a chemical vapor deposition method, and applying a compressive stress of 100 to 1,100 MPa to the outer layer.